When a user equipment (UE) has suspended its packet switched (PS) service (e.g., when UE performs CSFB to GERAN, which doesn't support Dual Transfer Mode, a common scenario, the UE is unable to communicate with a network entity in the PS core network. In this case, it is not optimal if the Policy Charging Control (PCC) node initiates some updates for the UE context or the active Packet Data Network (PDN) connection to that triggers signaling towards the UE that fails. In general, the PCC node may need to use UE status information of different kinds in addition to the reachability status of the UE.
The PCC system is unaware of UE mobility status information. Furthermore, when the system becomes more complicated, this principle proves inefficient. An example of this inefficiency is seen in the handling of the UE when suspended. For example, CSFB or SRVCC are existing features, however, there is no specific handling when UE gets into suspend state except the MME/SGSN informing the SGW/PGW about the suspension. Furthermore, there is no specific handling when UE gets into a power saving state only other than mobility management node holding such information. Additionally, the same problem would occur when the UE is in radio shadow and the MME has cleared the PPF flag due to not being able to page the UE.
When the UE is not reachable by the Packet Core Network (e.g., UE is in a suspend state, or UE is in a power saving state, or the serving MME/SGSN has cleared PPF flag for the UE) the UE can't be reached. Thus, in this situation, there is no reason for the PCC node to trigger bearer modifications. One such signaling case is PCRF initiated QoS modification. When the PCRF indicates to the PGW over the Gx interface that a QoS modification is needed, the PGW initiates an Update Bearer Request towards the UE via the SGW and the MME/SGSN. However, this Request will fail due to the UE condition of not being reachable for paging (i.e., UE is not listing for pages). This causes unnecessary signaling in the network system. Furthermore, the QoS change requested by the PCC may not be effectuated and the PCC and the EPC systems may be un-synchronized.